Rotary drill bits can be used in blast hole drilling. In general, blast holes have a depth in the range of about 50 to about 150 feet and are filled with a blasting material for breaking up the earth during mining operations. The body of the drill bit typically used for drilling blast holes is attached to a drill pipe by a threaded member on the body of the bit. The drill pipe is supported and rotated by a drilling rig. The body of the drill bit typically has three legs, each of the legs having a projecting, conical cutter-receiving journal. Three conical cutters, each having an axially extending recess open at one end, are rotatably mounted on respective journals with the use of friction reducing bearings interior to the conical cutters. Each conical cutter has rock cutting teeth or inserts on the outer surface of the conical cutter. The weight of the drill pipe above the drill bit and the rotation of the drill bit cause the conical cutters to independently rotate about their individual journals and cut through the earth.
Many drill bits have a central passageway which extends from the top to the bottom of the bit. A plurality of branch passageways extend from the central passageway and terminate at the bearings. These various branch passageways conduct air or other gas to the bearings to cool the bearings and to wash away drilling debris. Jet nozzle exits are generally located at the bottom of the drill bit adjacent to the conical cutters. Air or other gas discharged from the nozzles washes drilling debris away from the conical cutters and out of the drill hole.
During drilling operations, the resulting drilling debris creates a lot of dust. Such dust pollutes the air and can be a health hazard to workers in the area. Drilling equipment or other equipment may also be damaged by the dust. In order to reduce this dust, water or some other liquid can be mixed in with the air or other gas traveling through the central passageway in the drill bit, so that the liquid in this gas-liquid mixture exits the jet nozzles and suppresses the dust. However, the gas-liquid mixture also travels to the bearings and the liquid in the mixture can be harmful to the bearings. Water can corrode the bearings creating corrosion pits which can lead to cracking of the bearings.
In order to reduce the problem of water corrosion in the bearings, many drill bits which provide for the gas-liquid mixture traveling down the central passageway have a gas-liquid separator which separates the liquid from the gas so that only gas travels through the bearings. The separated liquid, on the other hand, exits through the jet nozzles and suppresses the dust. U.S. Pat. No. 3,788,408 by Dysart provides an example. The patent discloses different embodiments where a baffle element deflects a gas-liquid mixture. Due to the velocity of the gas-liquid mixture, the deflection of the gas-liquid mixture around the baffle separates out an at least substantially liquid free gas stream. Part of the gas undergoes a change in direction toward the bearings while the inertia of the heavier liquid causes it to continue on with the remaining gas-liquid mixture and exit through the jet nozzle. The at least substantially liquid free gas stream travels into the passageways leading to the bearings. However, a problem is that not all of the liquid is prevented from traveling to the bearings. Liquid can splash, for example because of turbulence in the gas-liquid mixture, into the passageway leading to the bearings.
It is an object of this invention to provide an improved apparatus for separating liquid from gas in a drill bit where the separated gas cools and cleans the bearings and the separated liquid suppresses dust in the drilling environment. It is a further object to minimize the amount of liquid which travels to the bearing of the drill bit.